<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        *{
            margin: 0;
            padding: 0;
        }
        body{
            background:url(https://img.zcool.cn/community/01714a5c5901b1a801203d223f67e1.jpg@1280w_1l_2o_100sh.jpg) no-repeat;
            background-size: cover;
            height: 100vh;
        }
        #canvas{
            margin: auto;
            display: block;
            box-shadow: 0 5px 5px rgba(0, 0, 0, .5);  
            background: rosybrown;
        }
    </style>
</head>
<body>
    
    <canvas id="canvas"></canvas>

    <script>
        var canvas = document.querySelector("#canvas");
        var WIDTH = 500, HEIGHT = 700;

        canvas.width=WIDTH;
        canvas.height=HEIGHT;

        var ctx = canvas.getContext('2d');

        ctx.moveTo(100,100)
        ctx.lineTo(300,300)
        ctx.strokeStyle = 'gold'
        ctx.lineWidth=5

        ctx.stroke()

        ctx.beginPath()
        ctx.arc(40, 40, 20, 0, 1.5 * Math.PI, 2 * Math.PI)
        ctx.strokeStyle = 'black'
        ctx.lineWidth = 1
        ctx.stroke()
    </script>
</body>
</html>